Inertia switch



Jan. 5, 1960 J. RABINOW ETAL INERTIA SWITCH 2 Sheets-Sheet 1 Filed Dec. 16, 1943 NIH DIRECTION OF ACGELERflT/ON JACOB kNVENTORS LL/AM B "CLEAN ATTORNEY I United States Patent INERTIA SWITCH Jacob Rabinow and William B. McLean, Washington, D.C., assignors to the United States of America as represented by the Secretary of the Navy This invention relates to circuit making and breaking devices and more particularly to a novel inertia-operated switch for use with an electrical device, such as a fuze, in an explosive projectile. The new switch operates upon sustained acceleration of the projectile in flight to close an arming circuit, and upon substantial cessation of the acceleration closes a second arming circuit, whereby the switch provides a dual safety factor.

In a projectile having an electrical fuze employing an electronic tube, it is important for the sake of safety to delay the arming of the device until the projectile has traveled a certain distance from the operator, and to allow time for the heating of the electronic tube. In this Way, premature explosions resulting from the shock of firing or from rough handling may be avoided, and the heating of the electronic tube assures that the electrical fuze will be in operating condition at the desired time.

An object of this invention is to provide a switch which closes a circuit when acted upon by a force of setback and, after a predetermined time interval and' after substantial cessation of the force of setback, closes a second circuit.

Another object of the invention is to provide an inertiaoperated device having a plurality of switches and means including a spring for operating one of the switches, but only after another of the switches has been operated. By means of detents, actuation of the subsequently operating switch is positively prevented until after actuation of the first switch.

Another object of the invention is to provide a device of the character described which will be actuated only upon sustained acceleration and which will not be operated accidentally, as by dropping or jolting. Resilient means connected to the switch which tends to operate first prevents operation of that switch except at the end of -a sequence after sustained acceleration, and returns the switch to its initial position after the device is acted upon by an acceleration of insuflicient duration or degree to operate the device, thus preventing operation of the device by the cumulative effect of minor accelerations.

A further object of the invention is to provide a device of the character described which is simple and compact in construction and positive in operation.

These and other objects of the invention will be apparent from the following description and the accompanying drawings, in which:

Fig. 1 is a plan view of one embodiment of the invention for use in a projectile fuze, showing the parts in their initial positions with the switches open;

Pig. 2 is a view similar to Fig. l but showing the parts after the first switch has closed and prior to the closing of the second switch;

Fig. 3 is an elevation of the left end of the device shown in Fig. 1;

Fig. 4 is an elevation of the right end of the device shown in Fig. 1;

2,920,157 Patented Jan. 5, 1960 ice Fig. 5 is a view similar to Figs. 1 and 2 but with the parts in their final positions;

Figs. 6, 7 and 8 are cross-sectional views taken on lines 66, 7-7 and 88, respectively, of Fig. l; and

Fig. 9 is a perspective view of the resilient catch which retains the first-operated switch in closed position.

Near insulating member 11, a stub shaft 23 protrudes from plate 10, a sleeve 24 being rotatably mounted on the shaft. Keyed to sleeve 24 is an insulating element 25 which carries an electrically conducting bridge member 26 adapted to bridge contact members 17 and 18 to complete the electrical circuit across those members. Also keyed to and rotatable with sleeve 24 is an inertia member or element 27 which is shaped as a segment of a disc. The inertia member 27 is urged in a counterclock-wise direction by spring 28 which is keyed to the end of shaft 23 and is attached to post 29 on the inertia member. Inertia member 27 has a flange 30 extending downwardly toward plate 10 from its periphery and has a lug 43 extending outwardly from its periphery. Inertia member 27, sleeve 24, insulating member 25, and bridging member 26 are urged by spring 28 in a counterclockwise direction toward a position in which bridging member 26 bridges contact members 17 and 18.

Near insulating member 12, a stub shaft 31 is mounted on plate It and carries a sleeve 32 rotatably mounted on the shaft. Keyed to and rotatable with sleeve 32 is an insulating member 33 which carries electrically conducting bridge members 34 and 35 adapted to bridge contacts 1920 and 21-22, respectively. Also keyed to and rotatable with sleeve 32 is an inertia member or element 36 which overlaps the element 27 and, like element 27, is shaped as a segment of a disc and has a flange 37 extending upwardly from a portion of its periphery. By means of a spring 38 keyed to the end of shaft 31 and attached to a post 39 on inertia member 36, the inertia member, sleeve 32, insulating member 33, and bridge members 34 and 35 are urged in a clockwise direction toward the open circuit position shown in Fig. 1.

Plate 10 has a slot 40 into which extends a resilient latch 41 attached to the underside of plate 10. Latch member 41 is positioned so as to engage shoulder 42 on inertia member 36 when the latter is in its closed circuit position.

In operation, the parts of the device are initially in the positions shown in Fig. 1, all switches being open. Inertia member 36 is at its extreme position of clockwise movement abutting screw 16 due to the action of spring 38. Spring 28 tends to move inertia member 27 in a counter-clockwise direction to close switch 1718 but is prevented from doing so by the engagement of lug 43 on the periphery of member 27 with flange 37 on the periphery of inertia member 36. Member 36 is, in turn, held against counter-clockwise rotation by the abutment of the counter-clockwise end of flange 37 with flange 30 of member 27. This interlock between elements 27 and 36 which, because of the mutual interengagement and interaction, establishes a time period for sequential circuit closure as is more thoroughly explained below.

The portions 30, 37, therefore, comprise timer means which cause the delayed action of element 36 for the initial circuit closure.

When the device is accelerated in the direction of the arrow in Fig. 1, due to firing a projectile containing it, a force of setback acts upon the device, immediately rotating member 27 in the clockwise direction and later rotating member 36 in a counter-clockwise direction. As explained above, member 36 is initially prevented from rotating under the actuation of setback by engagement of the end of its flange 37 against flange 30 of inertia member 27. The member 27, however, is initially free to rotate in the clockwise direction, and does so because of the slip fit between flanges 37 and 30, when acted upon by setback as stated above, moving to the position shown in Fig. 2, its rotation being limited by screw 13. As soon as flange 30 of member 27 is clear of flange 37 of member 36, the latter is belatedly free to rotate in the counter-clockwise direction under continuing actuation of setback, in other words, sustained acceleration, and moves under its influence in that direction to the position shown in Fig. 2 in the interim between the setback and retrogressive movements of element 27, being halted in its counter-clockwise rotation by contact with screw 15. When element 36 reaches its extreme position of counter-clockwise rotation, the bridge members 34 and 35 bridge contact members 1920 and 21-22, respectively, thus closing at least a first circuit but actually two circuits, which may be, for example, A and B battery circuits. When shoulder 42 of the inertia member 36 rotates past resilient catch 41 in the counter-clockwise direction, it will upon settling back be held by the catch 41 against return to the position which it occupied in Fig. 1. In this way, the switches which are closed by rotation of element 36 are maintained in a closed condition.

As soon as flange 37 of inertia member 36 has advanced to a position in which it no longer lies in the path of detent 43 or flange 3b of inertia member or element 27, the latter is free to rotate under the actuation of spring 28 in a counter-clockwise direction to the closed circuit position which it occupies in Fig. 5, and it assumes this position immediately upon substantial cessation of acceleration, being halted in its rotation by screw 14. Member 27 thus comprises an'interruptedly operable element for the movements of which the setback and spring (28) actions constitute successive but diverse operating forces. The switch 26 corelated with it does not respond to the initial movement by setback but does respond with a circuit closure on the alternate movement of the element 27 by spring force. In the position of element 27 in Fig. 5, bridge member 26 engages contacts 17 and 18 and closes the second electrical circuit, which may be, for example, a thyratron circuit.

Once member 27 has retrogressed in the counterclockwise direction to a position wherein its flange 30 lies in the path of flange 37, the clockwise rotation of element 36 to an open circuit position would be prevented by the engagement of flange 37 with flange 30, in case of a failure of resilient latch 41. If desired, the spring 28 may be made sufliciently stronger than spring 38 to insure rotation of element 27 to a position in which its flange 30 prevents clockwise rotation of element 36 prior to the clockwise rotation of member 36 upon cessation of acceleration, thus doing away with the need for the resilient latch 41. If the latch is used, rotation of element 27 may be retarded by an escapement or other delay device, if desired, in order to provide an additional time delay before the closing of the thyratron circuit across contacts 17 and 18.

By the provision of the novel interlocking features involving flanges 3i and 37 and detent 43, I have achieved a novel inter-relation between a plurality of switches in an inertia operated device, whereby the operation of one switch is positively postponed until after the operation of another switch.

The plurality herein contemplated is not necessarily limited to the two elements 27, 36 disclosed, but may be extended to a series comprising more than two. The fundamental principle would prevail, namely, that each inertia operated element is restrained by a spring against inertia operation, and is so interlocked with the element next in succession as to insure sequential operation when the force of inertia endures long enough, but on the other hand will insure resetting of the elements to their initial positions by the springs in case the force of inertia is of shorter duration than required to actuate the switch at the end of the element series.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

We claim:

1. In an inertia operated device for a projectile, means responding to sustained acceleration of the projectile in flight for closing a first electrical circuit, means operative upon a substantial cessation of acceleration and only after closing of said first mentioned circuit to close a second electrical circuit, and an escapement mechanism controlling said first means to defer the closure of said first circuit.

2. In an inertia operated device, two switches, one of said switches being operable by setback, spring means for actuating the second switch, and cooperative means on said switches for preventing actuation of said spring actuated switch until after actuation of said setback actuated switch.

3. In an inertia operated device, a switch operable by setback, 21 second switch, biasing means for operating the second switch, and means movable with said first named switch cooperative with said second named switch for preventing closing of said second named switch by said biasing means until after operation of said first named switch.

4. In an inertia operated device, a rotary switch operable by setback, a second rotary switch, a spring for operating the second switch, and means for securing said spring operable switch against circuit closure until after operation of said setback operable switch.

5. In an inertia operated device, a switch operable by setback, a spring operable switch, means for securing said setback operable switch in the position it assumes upon sustained acceleration of the device, and means for securing said spring operable switch against operation until subsequent to actuation of said setback operable switch.

6. In an inertia operated device, a rotary setback operable switch, a rotary spring operable switch, a flanged member rotatable with said spring operable switch, and a detent on the periphery of said last named flanged member whereby said spring operable switch is secured against rotation until subsequent to the operation of said setback operable switch.

7. In an inertia operated device, a rotary setback operable switch having a flanged member, a rotary spring operable switch having a flanged member, and a detent on said last named flanged member engaging said first named flanged member to secure the spring operable switch against rotation by spring operation until subsequent to the operation of said setback operable switch.

8. In an inertia operated arming device for use in a projectile, two pairs of contacts, a bridging member rotatable by a force of setback to close a circuit across a pair of said contacts, a second bridging member, biasing means for rotating said last member to close a circuit across the second pair of said contacts, and means for securing said last named bridging member against rotation to a closed circuit position until subsequent to rotation of said setback rotatable bridging member to a closed circuit position.

9. In an inertia operated arming device for use in a projectile, two pairs of contacts, a bridging member rotatable by a force of setback to close a circuit across a pair of said contacts, a second bridging member, biasing means for rotating said last member to close a circuit across the second pair of contacts, means for securing said last named bridging member against rotation to a closed circuit position until subsequent to the otation of said setback rotatable bridging member to a closed circuit position, and means for retaining said setback rotatable bridging member in its closed circuit position.

10. In an inertia operated arming device for use in a projectile, two pairs of contacts, a bridging member rotatable by a force of setback to close a circuit across one pair of said contacts, a flanged member rotatable with said bridging member, a second bridging member, a spring for rotating said last member to close a circuit across the second pair of said contacts, and a flanged member rotatable with said spring-actuated bridging member, said flanged members being located with respect to each other so as to secure said spring-actuated bridging member against movement to its closed circuit position until subsequent to movement of said setback actuated bridging member to its closed circuit position and to retain said setback actuated bridging member in its closed circuit position.

11. In a switch, a plurality of inertia operated elements, springs restraining each of said elements in opposition to the action of inertia, interlocking means on said elements insuring sequential operation of said elements under the action of inertia, and a switch operatively related to the element last operated in said sequential operation, the arrangement of said interlocking means being such that the springs will reset the elements to their initial positions in the event of insufficiency of inertia duration for complete sequential operation.

12. In an inertia operated switch, a pair of movable elements commonly influenced by the force of inertia, mutually engaging means on the elements checking the first element from movement by said force but allowing the second element to yield to said force during the time period of interengagement at the end of which the first element is released from said engaging means to yield to said force, means acting upon the second element at a substantial cessation of inertia force to countermove the second element, and switch means which are parts of the respective first and second elements, producing sequential circuit closures after the first element is released.

13. In an inertia operated switch, a pair of movable elements commonly influenced by force of inertia, timer means consisting of portions on each element inter- 6 engaging for an established period to temporarily check one element while allowing movement of the second element during acceleration of the switch, disengagement of said portions ensuing said period allowing movement of the first element during sustained switch acceleration, a spring bearing on the second element, being overpowered by said acceleration but acting during eventual deceleration of the switch to countermove the second element, and switch means combined with each of the elements, producing sequential circuit closures at the ends of movement and countermovement of the respective first and second elements.

14. In an inertia operated switch, a pair of overlapped movable elements commonly influenced by force of inertia, timer means consisting of portions on each element, intersecting for mutual interengagement thereby to check one element while allowing movement of the second element through a period determined by the duration of interengagement of said portions during acceleration of the switch, disengagement of said portions ensuing said period allowing movement of the first element during residual switch acceleration, a spring bearing on the second element, being overpowered by said acceleration but acting during eventual deceleration of the switch to countermove the second element, and switch means combined with each of the elements, producing sequential circuit closures at the ends of movement and countermovement of the respective first and second elements.

. 15. In an inertia operated switch adapted to be accelerated in one direction, a pair of interacting switch elements sequentially movable into closing positions of separate circuits, timer means controlling the sequential movement, including an engaging member on one element and an arcuate flange on the second element, the engagement of said member with said arcuate flange resulting from the switch acceleration and serving to temporarily check said one element while allowing relative idle movement of the arcuate flange and its second element to a point of disengagement of said member from said arcuate flange and allowing movement of said one element to the primary circuit closure during sustained acceleration, and a spring acting on the second element becoming effective during eventual deceleration of the switch to countermove the second element to the secondary circuit closure.

References Cited in the file of this patent UNITED STATES PATENTS 2,081,662 Farmer May 25, 1937 2,152,256 Hewitt Mar. 28, 1939 2,236,959 Salmond et a1. Apr. 1, 1941 

